Golf club shaft and golf club

ABSTRACT

According to an aspect of this invention, there is provided a golf club shaft including a prepreg containing a carbon fiber, wherein the prepreg is winded and cured, and a winding thickness of the prepreg on a striking face is larger than a winding thickness of the prepreg on any other portion.

BACKGROUND

1. Field of the Invention

The present invention relates to a golf club shaft, and morespecifically, to a golf club shaft made of fiber-reinforced resin.Further, the present invention relates to a golf club having the golfclub shaft.

2. Description of the Related Art

Golf club shafts may be classified into what are called a steel shaftsand carbon shafts. The carbon shaft is widely used in view of lightness,the high degree of design freedom and the like.

The carbon shaft is made of fiber-reinforced resin in which a carbonfiber is used as a main fiber. As a method of manufacturing the carbonshaft, a sheet winding method is known (see JP-A-2010-259694). In thismanufacturing method, a prepreg sheet is wound on a mandrel (core bar)and a wrapping tape is further wound thereon. Then the prepreg is heatedto be cured, thereby making the carbon shaft.

Since a golf club has large kinetic energy as a head end on which a headis fixed is heavy, it is possible to give a large initial velocity to aball at the time of swing, thereby making it possible to increase acarry of the ball. However, if only the head end is heavy, the center ofgravity of the club is excessively inclined to the head end, and thus,the swing becomes hard. For this reason, when the head end of the shaftis made heavy, a grip end of a base is also made heavy. Further, if thehead end and the grip end are heavy in this way and an intermediateportion is light, a follow-through at the time of swing is enhanced. Inthis way, in the golf club, since the carry of the ball and the swingperformance are changed according to the weight distribution on the headend and the grip end, the weight adjustment on both the sides has beenperformed at the time of golf club design in the related art.

Since the weight adjustment becomes different according to physicalstrengths or preferences of players, it is necessary to prepare variousheads and shafts. However, to prepare the various heads and shaftshaving different weights causes an increase in manufacturing cost andstorage cost. Thus, the weight adjustment has been performed by a simplemethod in which a plurality of types of heads and shafts havingdifferent weights are made, and then, a lead plate is attached to thehead in a case where the head end is heavy and a lead plate is attachedto the inside of the grip of the shaft in a case where the grip end isheavy.

If the weight on the grip end of the carbon shaft is made heavy due tothe lead plate attachment, the weight of the shaft is lighter than thatof a metal shaft made of a metallic tube in the related art. Further,since the lead plate having a large specific gravity can be only locallyattached, it is difficult to increase the weight of the entire grip end,and thus, the rotational moment is changed according to the gripposition of a player.

SUMMARY

An object of the invention is to provide a golf club shaft in which theweight on the striking face is increased by distributing, on thestriking face, a large amount of prepregs where carbon fibers aredistributed, and a golf club that uses the golf club shaft.

According to an aspect of the invention, there is provided a golf clubshaft including a prepreg containing a carbon fiber, wherein the prepregis winded and cured, and a winding thickness of the prepreg on astriking face is larger than a winding thickness of the prepreg on anyother portion. By increasing the weight of the striking face in thisway, it is possible to dispose the center of gravity on the strikingface and to achieve a golf club having a small moment for easy swing.Further, even though the weight of the head is increased, it is possibleto achieve a golf club having a balance that is not different from thatof a golf club in the related art.

By increasing the winding thickness of the prepregs on the head endcompared with the winding thickness of the prepregs in the intermediateportion, it is preferably possible to increase the strength on the headend;

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingwhich is given by way of illustration only, and thus is not limitativeof the present invention and wherein:

FIG. 1 is a diagram illustrating winding of prepregs.

FIG. 2A is a side view of a mandrel,

FIG. 2B is a cross-sectional view of prepregs wound on the mandrel, and

FIG. 2C is a cross-sectional view of a shaft in a length direction.

FIGS. 3A and 3B are perspective views of a golf club and a shaftthereof.

FIG. 4 is a plan view of a prepreg.

FIG. 5 is a plan view of prepregs.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the invention will be described withreference to the accompanying drawings.

FIG. 1 and FIG. 2 are diagrams illustrating a method of manufacturing agolf club shaft according to an embodiment of the present invention.FIGS. 2A to 2C are enlarged views schematically illustrating a mandrel10 and prepregs wound in a radial direction.

In the manufacturing method, the mandrel 10 and prepregs 11 to 21 areused. A central axis line of the mandrel 10 is a straight line. Theshape of a cross section perpendicular to the central axis line of themandrel 10 is circular. As shown in FIG. 2( a), the mandrel 10 has ataper in which a head end (head side) is thin and a striking face (gripend) is thick, but may have an equivalent radial portion of which thediameter is partially constant.

Preferably, after a parting agent is coated on the surface of themandrel 10, the prepregs 11 to 21 of a sheet shape are sequentiallywound. The prepregs 11 to 21 include a carbon resin and a matrix resin.

In the present embodiment, in the prepregs 11, 14, 16, 18, 19, 20 and21, fibers are orientated in a straight direction, that is, in a shaftlength direction. In the prepregs 15 and 17, fibers are oriented in ahoop direction, that is, in a shaft circumferential direction. Here, thefibers of the prepreg 19 may be in the hoop direction. In the prepreg12, the fibers are oriented in a biased direction of +45° (directionoblique to the shaft length direction), and in the prepreg 13, thefibers are oriented in a biased direction of −45°. Here, the fibers ofthe prepreg 12 may be oriented by the angle of −45°, and the fibers ofthe prepreg 13 may be oriented by the angle of +45°. Further, the biaseddirection is not limited to 45°, and may have the range of 30° to 60°.

The prepregs 11 and 14 to 21 have a width to be wound on the outercircumference of the mandrel 10 by one round. The prepregs 12 and 13have a width to be wound on the outer circumference of the mandrel 10 bya plurality of rounds, for example, 2 to 5 rounds.

The prepregs 12, 13, and 15 to 19 have a length extending over theentire length of the shaft. The prepregs 11, 20 and 21 have a length of8% to 20% of the entire length of the shaft, and particularly, a lengthof about 10 to about 15% thereof to be distributed only on the head endof the shaft. By winding the prepregs 11, 20 and 21, the windingthickness of the head end is increased. The prepreg 21 has a triangularshape in which the width becomes large as it goes to the head end, andthus, the vicinity of the head end of the shaft has a cylindrical shapeof an approximately uniform diameter. The vicinity of the head end isinserted into a hosel hole of a head.

The prepreg 14 is distributed only on the striking face, and the lengththereof in the shaft length direction is preferably 15% to 45% of theentire length of the shaft, particularly, 20% to 40%, and moreparticularly 25% to 35%. By selecting the number of the prepregs 14, thewinding thickness of the striking face is increased, as shown in FIG.2B.

It is preferable that the thicknesses of the prepregs 12 and 13 be 0.125mm or less, and particularly, about 0.05 mm to about 0.1 mm. It ispreferable that the thicknesses of the prepregs 15 and 17 be 0.1 mm orless, and particularly, about 0.02 mm to about 0.05 mm. It is preferablethat the thicknesses of the prepregs 16, 18 and 19 be 0.125 mm or less,and particularly, about 0.05 mm to about 0.1 mm. It is preferable thatthe thicknesses of the prepreg 14 be 0.05 mm to 2.0 mm, andparticularly, about 0.075 mm to about 0.15 mm. It is preferable that thethicknesses of the prepregs 11, 20 and 21 be 0.05 mm to 0.2 mm, andparticularly, about 0.075 mm to about 0.15 mm.

It is preferable that the volume fraction of fibers in the respectiveprepregs 11 to 21 be 60 vol % to 80 vol %, and particularly, about 70vol % to about 75 vol %. It is preferable to use an epoxy resin or thelike as the resin.

It is preferable that the tensile elasticity of the carbon fibers in theprepregs be 10 ton/mm² to 46 ton/mm² in the case of the straightdirection, and particularly, about 20 ton/mm² to about 40 ton/mm².Further, it is preferable that the tensile elasticity thereof be 8ton/mm² to 30 ton/mm² (about 78.4 GPa to about 294 GPa) in the case ofthe hoop direction, and particularly, about 10 ton/mm² to about 24ton/mm². It is preferable that the carbon fibers oriented in the biaseddirection have a high modulus elasticity of 40 ton/mm² (about 392 GPa)or more, for example, 40 ton/mm² to 55 ton/mm².

In a case where the prepregs 11 to 21 are wound on the mandrel 10, theprepregs 11 to 21 may be wound one by one, or may be wound while pastinga part of the prepregs. For example, the prepregs 15 and 16 may bepasted together, or the prepregs 17 and 18 may be pasted together. Anoperation of winding the prepregs 11 to 21 on the mandrel 10 may bemanually performed, or may be performed by a winding machine (alsoreferred to as a rolling machine). After the prepregs 11 to 21 are woundon the mandrel, a wrapping tape winding process is performed. Althoughnot shown, the wrapping tape is wound in a spiral shape.

After the winding process, a curing process is performed by heating, andthus, the matrix resin in the prepregs is cured.

After the curing process, extraction of the mandrel and removal of thewrapping tape are performed, to thereby obtain a cured tubular body(element tube). The opposite ends of the element tube are cut asnecessary and are ground, to thereby obtain a golf club shaft 3 (seeFIG. 3B). Then, a head 2 and a grip 4 are mounted to the golf club shaft3, to thereby obtain a golf club 1 (see FIG. 3A).

In the shaft 3, it is preferable that the thickness of the rearmost endof a striking face 3 c be 2.5 mm to 1.0 mm, and particularly, 0.6 mm to0.8 mm. It is preferable that the thickness of the head end of a headend 3 a is 1.3 mm to 1.8 mm, and particularly, 1.4 mm to 1.7 mm.Further, it is preferable that the average thickness of an intermediateportion 3 b is 0.4 mm to 0.7 mm, and particularly, about 0.5 mm to about0.65 mm. It is preferable that the thickness of the rearmost end of thestriking face 3 c be larger than the average thickness of theintermediate portion 3 b by 0.1 mm to 0.4 mm, and particularly, by 0.125mm to 0.3 mm. By increasing the thickness of the striking face 3 c inthis way, the weight of the shaft 3 on the striking face is increased.It is preferable that a range L of the striking face 3 c having a largethickness be 15% to 45%, particularly, 20% to 40%, and moreparticularly, 25% to 35% of the entire length of the shaft 3 from thestriking face of the shaft 3.

In the case of a shaft for a wood golf club, the entire length of theshaft is about 1050 mm to about 1220 mm. In the case of the wood golfclub shaft, it is preferable that the position of the center of gravitybe present in the range of 52% to 57% from the head end of the shaft 3on the head end. It is preferable that the weight of the shaft be about40 g to about 50 g. Further, in this case, the outer diameter of aregion that ranges from the head end to 250 mm be 8.9 mm to 9.5 mm. Itis preferable that a portion between the head end 3 a and theintermediate portion 3 b and a boundary portion between the intermediateportion 3 b and the striking face 3 c have a taper of about 6.5/1000 toabout 7.2/1000.

In this embodiment, since the thickness of the head end 3 a is largerthan that of the intermediate portion 3 b, the strength of the head end3 a is high.

The layering example of the prepregs in FIGS. 1 and is an example of theinvention, and thus, layering examples other than the example in FIGS. 1and 2 maybe used. For example, in FIG. 1, a prepreg in which the fibersare oriented in the hoop direction, that is the same as the prepreg 15(or 17), may be disposed between the prepregs 18 and 19 in which thefibers are oriented in the straight direction. Further, in FIG. 1, apart of the prepregs in which the fibers are oriented in the hoopdirection, for example, the prepreg 17 in FIG. 1 may be omitted.Further, the number of the prepregs 12 and 13 in which the fibers areoriented in the biased direction may be changed to 4 to 6 in total. In anormal case, it is preferable to layer three to five sheets of prepregs,other than the prepreg 14, in which the fibers are oriented in thestraight direction, one to three sheets of prepregs 14, two, four or sixsheets of prepregs in which the fibers ate oriented in the biaseddirection, and one to three sheets of prepregs in which the fibers areoriented in the hoop direction. In the present embodiment of theinvention, a prepreg 14A that is large in length in the hoop directionas shown in FIG. 4 may be used as the prepreg 14. Further, instead ofone sheet of prepreg 14, as shown in FIG. 5, a plurality of sheets ofprepregs 14 a, 14 b and 14 c may be used. In this case, the size of theprepreg wound outside may be decreased, as in the prepregs 14 a to 14 c.

In the above description, only the carbon fibers are included in theprepregs, but other fibers such as glass fibers, silicon carbide fibers,alumina fibers, aromatic polyamide fibers or boron fibers may be mixedtherein.

What is claimed is:
 1. A golf club shaft comprising a prepreg containinga carbon fiber, wherein the prepreg is winded and cured, and a windingthickness of the prepreg on a striking face is larger than a windingthickness of the prepreg on any other portion.
 2. The golf club shaftaccording to claim 1, wherein: the winding thickness of the prepreg onthe striking face is largest; the winding thickness of the prepreg on ahead end is second largest; and the winding thickness of the prepreg inan intermediate portion between the striking face and the head end issmallest.
 3. The golf club shaft according to claim 2, wherein thethickness of a rearmost end on the striking face is larger than anaverage thickness of the intermediate portion by 0.1 mm to 0.4 mm. 4.The golf club shaft according to claim 1, wherein the striking face isprovided in a range of 15% to 45% of an entire length of the shaft froman end of the striking face.
 5. The golf club shaft according to claim1, wherein: the golf club shaft is a golf club shaft for a wood club;and a position of center of gravity is present in a range of 52% to 57%of an entire length of the shaft from an end of the head end.
 6. A golfclub comprising: a golf club shaft comprising a prepreg containing acarbon fiber; and a club head connected with the golf club, wherein theprepreg is winded and cured, and a winding thickness of the prepreg on astriking face is larger than a winding thickness of the prepreg on anyother portion.